The present invention generally relates to the removal of residual materials from containers for disposal or recycling. More specifically, the present invention relates to a method and apparatus for cleaning residues from the surface of containers by the use of low temperatures. In addition, the present invention relates to a method and apparatus for reducing the bulk volume of containers by the use of low temperatures.
The disposal of wastes has become a great concern due to the environmental problems associated with hazardous materials. Of even more immediate concern are the economic problems associated with rising costs and reduced capacity of landfills, as well as the tighter governmental regulations facing waste generators. Consequently, disposal of containers and the residual materials remaining therein can be a costly and time consuming endeavor. Emphasis has been placed on cleaning the residues from the containers so that only the residues, and not the containers, are subject to costly hazardous waste disposal. This leaves the containers available to be reused, recycled, or disposed of in a less expensive non-hazardous waste landfill.
The U.S. government has established guidelines under the Resource Conservation and Recovery Act (RCRA) that specify the cleanliness requirements for disposal of containers as non-hazardous waste. Nevertheless, some states are imposing bans on the disposal of even clean containers in landfills as a remedy for rapidly diminishing landfill capacity. This leaves reuse or recycling of the containers as the only alternative.
A broad range of residues of expended commodities are subject to costly hazardous waste disposal. Some of these residues include, but are not limited to tars, lubricants, mastics, inks, coatings, solvents, adhesives, sealants, paints, etc. A range of traditional cleaning methods exists to remove such residues from commodity containers. These methods include applying water, steam, soaps, detergents, chemical solvents, abrasives and scrubbing equipment. All of these methods result in an increased volume of waste being created that may be more difficult to dispose of than the original residue. These methods may be costly due to the need of expensive materials, equipment and intensive labor. Even if the residue is not considered hazardous, there may be restrictions imposed by municipal sewage districts that require expensive pretreatment before the residue and wash liquid may be discharged into the sewage drains.
As an example of traditional cleaning methods, chemical solvent based cleaning involves numerous disadvantages. The solvents are expensive. They require special care and handling because of their combustibility, corrosiveness and/or volatility. Special ventilation equipment may be required to recover the volatile organic compounds which vaporize during use. Additional equipment may be needed to separate the solvent from the residue waste wash for recycling of the solvent. If not separated, the volume of the waste product is greatly increased. Employees require additional training to safely handle the equipment and materials. Special inspections, building codes and zoning requirements may be difficult to comply with, or require that special facilities be constructed for the cleaning equipment. In the end, most small organizations do not have the resources to properly handle the problems associated with disposing or recycling residue laden containers using traditional methods.
Even when the commodity containers are clean, the sheer bulk volume of the containers may make their disposal or recycling problematic. Storage and transportation costs are related to the bulk volume of the freight. Apparatus exists for the size reduction. This equipment is available for application to reduce the bulk volume of containers. However, this equipment is not without certain disadvantages.
Typically, the bulk volume of plastic containers is reduced by shredding the containers. Shredding equipment may be highly dangerous to operate, exposing personnel to severe injury if improperly used. The machinery may also be very expensive and require significant maintenance.
On the other hand, the bulk volume of metal containers is commonly reduced by compacting or crushing. This equipment may be less expensive than shredding machinery and safer to operate. The equipment applies a compressive force to crush and permanently deform the metal containers.
Unfortunately, compacting equipment designed to crush metal containers may not work satisfactorily with plastic containers having a degree of elasticity. Generally, plastic containers have a tendency to partially rebound to their original shape after the compressive forces are released. When a plastic container is removed from the compactor, it would return to near its original bulk volume.
Therefore, for the foregoing reasons, there is a need for a method and or apparatus for treating plastic containers so that they maintain a reduced bulk volume after release of compression forces that is safe, simple and cost effective.
In addition, there exists a sizable gap between existing traditional cleaning methods to remove residue from containers and the requirements of industry to clean containers with a cost effective, environmentally safe process. Therefore, there exists the need for a method and apparatus for cleaning residues from containers that does not have the inefficiencies, hazards and environmental liabilities associated with traditional cleaning methods.